From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752464AbaIUTgk (ORCPT ); Sun, 21 Sep 2014 15:36:40 -0400 Received: from mx1.redhat.com ([209.132.183.28]:21843 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752243AbaIUTgi (ORCPT ); Sun, 21 Sep 2014 15:36:38 -0400 Date: Sun, 21 Sep 2014 21:33:41 +0200 From: Oleg Nesterov To: Ingo Molnar , Peter Zijlstra Cc: Kirill Tkhai , Mike Galbraith , linux-kernel@vger.kernel.org Subject: [PATCH 3/3] sched: print_rq: don't use tasklist_lock Message-ID: <20140921193341.GA28628@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140921193316.GA28596@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org read_lock_irqsave(tasklist_lock) in print_rq() looks strange. We do not need to disable irqs, and they are already disabled by the caller. And afaics this lock buys nothing, we can rely on rcu_read_lock(). In this case it makes sense to also move rcu_read_lock/unlock from the caller to print_rq(). Signed-off-by: Oleg Nesterov --- kernel/sched/debug.c | 7 ++----- 1 files changed, 2 insertions(+), 5 deletions(-) diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c index c7fe1ea..ce33780 100644 --- a/kernel/sched/debug.c +++ b/kernel/sched/debug.c @@ -150,7 +150,6 @@ print_task(struct seq_file *m, struct rq *rq, struct task_struct *p) static void print_rq(struct seq_file *m, struct rq *rq, int rq_cpu) { struct task_struct *g, *p; - unsigned long flags; SEQ_printf(m, "\nrunnable tasks:\n" @@ -159,14 +158,14 @@ static void print_rq(struct seq_file *m, struct rq *rq, int rq_cpu) "------------------------------------------------------" "----------------------------------------------------\n"); - read_lock_irqsave(&tasklist_lock, flags); + rcu_read_lock(); for_each_process_thread(g, p) { if (task_cpu(p) != rq_cpu) continue; print_task(m, rq, p); } - read_unlock_irqrestore(&tasklist_lock, flags); + rcu_read_unlock(); } void print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq) @@ -331,9 +330,7 @@ do { \ print_cfs_stats(m, cpu); print_rt_stats(m, cpu); - rcu_read_lock(); print_rq(m, rq, cpu); - rcu_read_unlock(); spin_unlock_irqrestore(&sched_debug_lock, flags); SEQ_printf(m, "\n"); } -- 1.5.5.1